Thin film coatings are used for a variety of different applications including, for example, low-emissivity (low-E) or solar control coatings, antireflective (AR) coatings, anti-scratch coatings, etc. Such thin film coatings typically comprise a plurality of thin film layers, and each thin film layer typically includes one, two, or three different materials.
High-entropy alloys have been known and described since the mid-1990s, but they have only relatively recently become the focus of research in the materials science and engineering fields. As is known in the art, current high-entropy alloys typically include five or more metals, with the metals being included in equal or nearly equal quantities. These types of high-entropy alloys have desirable properties in that they tend to be heat stable and mechanically durable. Indeed, these types of high-entropy alloys have advantageous properties including their ability to survive high temperature processing, as well as good strength-to-weight ratios, fracture resistance, tensile strength, and corrosion and oxidation resistance.
High-entropy alloys tend to have better mechanical properties compared to traditional alloys. Current research relating to high-entropy alloys tends to focus on hard-facing coatings. The inventor has determined, however, that it would be desirable to use high-entropy alloys in optical coatings.
Certain example embodiments relate to alloy systems that can be used in optical coatings. These alloys systems are heat stable because of the extremely high entropic contribution to their free energies. A first material system that may be used in connection with certain example embodiments includes SiAlN with one or more (and preferably two or more) of elements such as Hf, Y, Zr, Ti, Ta, and Nb. A second material system that may be used in connection with certain example embodiments includes TiO, with one or more (and preferably two or more) of elements such as Fe, Co, Ni, Sn, Zn, and N. In both example material systems, the presence of four or more elements aids in increasing the entropic effect on high-temperature stability. The material systems may be high-index materials that can serve as a substitute for titanium oxide in layer stacks, in some example applications.
The thin films described herein may be used in applications including, for example, low-emissivity or solar control coatings, AR coatings, anti-scratch coatings, wear-resistant coatings, corrosion-resistant coatings, etc., as appropriate with the optics of the coating, the layer stack, and what is desired in the end-application. The thin films described herein may be used as the outermost layers in layer stacks, diffusion barrier layers, high-index layers, and/or the like.
Methods of making the coated articles disclosed herein also are contemplated.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.